Keyless entry systems have found great acceptance in the automotive field. Such systems employ a radio transmitter which comprises part of the vehicle's key or is carried by a key fob or pendant. (For ease of reference, the user's transmitter wherever located will be referred to herein as a "transmitter pendant" or simply a "pendant." Also, a key having a radio transmitter will be referred to as an "electronic key.") The transmitter pendant sends a coded signal to a receiver located in the vehicle. The receiver, in turn, activates one or more lock motors associated with the doors and/or trunk of the vehicle. Significantly, the adoption of such systems in the automotive field followed naturally from the use of electric lock motors. With such motors and associated hardware having been fully engineered, e.g., fully designed, tested, and cost optimized, it was relatively straight forward, both from an engineering and an economics point of view, to add a radio based system so that the locks could be operated remotely.
In contrast to the automotive field, most door locks used in other fields, e.g., most residential and commercial door locks, are manually operated. Here the existing engineering base has been directed to optimizing the details of the lockset mechanism to permit large scale production at low cost. Another important difference from the automotive field is the fact that most residential and commercial door locks operate by being rotated, while modern automotive door locks operate by being pulled.
Electrically operated door locks, including remotely operated locks, are, of course, known. See, for example, Johansson et al., U.S. Pat. No. 4,457,148; Austin, U.S. Pat. No. 4,465,311 (pneumatic operation); Beudat et al., U.S. Pat. No. 4,633,688; Uebersax, U.S. Pat. No. 4,745,785; Johansson et al., U.S. Pat. No. 4,770,012; Kerschenbaum et al., U.S. Pat. No. 4,800,741; Corder et al., U.S. Pat. No. 4,802,353; Abend et al., U.S. Pat. No. 4,833,465; Corder et al., U.S. Pat. No. 4,854,143; and Davis et al., U.S. Pat. No. 4,907,429. Such locks, however, are generally too complicated to be produced at a price suitable for widespread residential use. Moreover, such locks typically require special apertures in the door and/or the door jam and thus they cannot be used as replacements for existing locksets. As a result of these limitations, the use of electrically operated door locks has been limited to commercial doors which are specially designed and sell at a high premium compared to standard doors having manual locks.